With triple-digit heat and nearly nonexistent rainfall, Phoenix seems an unlikely spot to be this year's West Nile virus epicenter.
Yet Arizona is the only state where the mosquito-borne virus is an epidemic, federal health officials say.
Those swimming pools, plus irrigation canals that slice through parts of the city, patio misters and lush lawns have inadvertently turned neighborhoods into oases for mosquitoes.
So far this year, at least 290 of the nation's more than 500 West Nile cases were reported in Arizona. Three of the 14 deaths were in Arizona. Nearly all the cases have been in the state's most populous county, Maricopa, which includes the Phoenix metropolitan area.
State health officials estimate that at least 30,000 Arizonans may have the virus without knowing it. Some people never have symptoms. Only about 1 percent of West Nile victims develop the potentially dangerous inflammation of the brain or spinal cord — meningitis or encephalitis.
Last year was the first time the virus appeared west of the Continental Divide. It hit Colorado hard and drifted slowly into Arizona's northeastern tip, then down south. It is now spreading in California, where at least 116 cases have been reported and at least five persons have died.
Although Arizona doesn't have a lot of mosquitoes because of long stretches of 100-plus degree days, one type of mosquito thrives there: the Culex tarsalis. The species is one of the best carriers of West Nile virus. It does well in suburban settings, and likes to feed on humans.